The present invention relates to moulding equipment for concrete moulding machines of the kind which are typically used for the production of moulded items in the form of tiles and bricks for paving and wall constructions, and comprising a cell-divided under-part with cells which are open both upwards and downwards, and which define the desired basic shape of the individual tiles/bricks, and a corresponding upper-part which from an upper holding plate has downwards-extending pressure plungers which are formed with lower pressure plates which pass down into the respective underlying cells in the under-part, and can hereby be used for downwards ejection of the moulded items from the cells.
The manner in which the equipment is used is that the under-part is placed on a moulding board placed on a vibration table, with the upper-part lying in a raised position over the under-part. A concrete supply carriage is guided in along the upper side of the under-part in the space below the upper-part for the introduction of concrete down into the moulding cells and the full filling of said cells. Upon conclusion of the filling, the supply carriage is withdrawn and the upper-part is lowered until the said pressure plates ram down against the concrete surfaces in the respective moulding cells. Thereafter, the upper-part is used as a multi-pressure plunger for compression of the concrete mass in the individual moulding cells, which is effected under strong vibration of the moulding equipment for the separation of air from the concrete mass. The mould items are hereby compressed to the desired block shape and uniform thickness. Thereafter, the upper-part is held at its end height in relation to the under-part, and power is applied to the under-part for raising this up from the moulding board, whereby the mould items, which by the pressure maintained from the upper-part can not participate in this raising, will remain standing on the moulding board during the relevant forming of the mould items. When the forming is brought to an end by the displacement of the under-part up to a position in which its underside is raised at least to the level of the upper-part""s pressure plates, the half-firm mould items can be removed from the vibration table by being pushed out from the table after raising of the upper-part, after which a new moulding cycle can be started after the lowering of the under-part to the moulding board and the raising of the upper-part to its start position.
It is hereby important that in the forming phase, which consists of ejection of the mold items from the molding cells, the under-part is raised to an upper position in which its under-side just moves free of the under-side of the upper-part""s pressure plates, and herewith free of the upper-side of the mould items, so that these items can be guided out in the horizontal direction, while the same raising should preferably not be driven so far that the upper-part""s pressure plates are exposed down below the under-side of the raised under-part, since this can give rise to problems regarding the subsequent separation of these parts when a new moulding cycle is initiated, i.e. the upper-side of the pressure plates should not emerge from the lower ends of the moulding cells.
The latter problems are particularly that when in the separated condition, the upper-part""s pressure plates and the under-part can be displaced in the horizontal direction in relation to one another, so that before the feeding back of the under-part and displacement of the upper-part to the start position, the pressure plates are not positioned opposite the corresponding holes in the under-part, whereby the displacement of the under-part to the start position is not immediately possible without manipulation of the mould parts.
Moreover, the relevant moulding machines should be able to work with moulding equipment with under-parts which have different heights for the formation of mould items with different desired heights (thicknesses), and therefore it is inexpedient to work with special settings of the machine functions, including the extent of the raising of the under-part in connection with the forming.
Especially in the changeover from moulding of items with great thickness to the moulding of items with relatively modest thickness, where the height of the under-part is modest, the adjustment of the machine functions for raising and lowering of the under-part will be relevant in order to prevent the upper-part""s pressure plates from being exposed down below the under-side of the raised under-part.
With the invention it has been realised that it is possible to avoid the above-mentioned problem concerning relative horizontal displacement between the upper part and the under-part during the forming of mould items, without special setting of the machine functions, by providing the upper-part or alternatively the under-part with means which ensure that the pressure plates maintain their position opposite the cells in the under-partxe2x80x94or their guiding engagement with the sides of the corresponding cellsxe2x80x94when the under-part is raised to a certain minimum height which is greater than the thickness of the mould items.
A preferred embodiment of said means for controlling the mutual positioning between the pressure plates and the cells corresponding therewith, where the moulding equipment is used both for the moulding of items with small thickness as well as items which are considerably thicker in relation hereto, is characterised by the upper-part being provided with at least one guiding pressure plate which is configured with an upwards extension, so that it maintains guiding engagement with the sides of the corresponding cells in the under-part when this is raised to a certain minimum height which is greater than the thickness of the thinnest or lowest under-parts.
Since the pressure plates are secured in the upper-part and can not be displaced in relation to one another, it is thus achieved that providing only one of the pressure plates is held in engagement in its corresponding cell in the under-part, the remaining pressure plates will thus be guided into their respective corresponding cells in the under-part when this is lowered again.
Without renouncing other embodiments of the invention, an embodiment of a guiding pressure plate can consist of a pressure plate with an increased thickness in relation to the remaining pressure plates in the upper-part.
With vertical displacement of the under-part (within limits defined by the thickness of the guiding pressure plate), the guiding pressure plate will hereby maintain its engagement in the corresponding cell, even though the upper-sides of the remaining pressure plates are lying at a level below the upper-side of the under-part.
Since it is the engagement of only the periphery of the pressure plate with the walls of the corresponding cell which is decisive for correct guiding between the upper and lower part, an alternative, preferred and material-saving embodiment of the guiding pressure plate will consist of a pressure plate having an upper-side along the periphery, or at least partly on opposite sides of the periphery, which is provided with an upright edge with an outer periphery which is coincident with the periphery of the pressure plate.
There is hereby achieved the same effect as that when the guiding pressure plate is configured with an increased thickness, but a considerably saving in material is achieved.
There are normally certain tolerances between the upper-part and the lower-part in said moulding machines, and with regard to this it will be preferred that the upper-part comprises at least two or more guiding pressure plates according to the invention. With small tolerances, there will thus be a need for a greater number of guiding pressure plates than with large tolerances.
As already mentioned, the relevant moulding machines should be able to work with moulding equipment which have under-parts of different heights for the formation of tiles/bricks with different desired heights, and therefore it is inexpedient to work with special settings of the machine functions, while it is a simple task to provide stop surfaces directly between the upper and under-part of a given moulding equipment, such that these parts can be allowed to be brought together to an extent that the upper-part""s pressure plates will simply not be able to emerge in the space below the under-side of the raised under-part.
It is well-known that such stop surfaces are established by welding downwards-extending pressure pins in the corner areas of the top plate of the upper-part, said pins being of such a length that they will ensure a relevant maximum extent to which the upper and lower-part of the moulding equipment can be brought together, in that they will be hit by corresponding areas of a protruding top-plate on the under-part when this is raised for the releasing of the mould items.
It has been ascertained that in order to achieve a relatively long operative lifetime, the relevant stop pins shall be fastened by particularly robust welds, the reason being that at their fastening they are exposed to a considerable weakening effect as a consequence of the strong vibrations and shock effect during the forming phase, to which they are exposed during every single operative cycle of the moulding equipment.
In light of this, with a second preferred embodiment of the means for the guiding and mutual positioning between the pressure plates and the cells corresponding herewith according to the invention, a better and cheaper solution has been sought, and surprisingly it has been found that such a solution can continue to be based on the xe2x80x9cstop-pin principlexe2x80x9d, merely with the modification that the stop-pin is not secured by welding, but appears as a threaded spindle which extends through a hole in the associated support plate and is fastened to this by the tightening of a nut, i.e. as a simple bolt fastening. Comprehensive tests have shown that a bolt fastened in this manner is far better able to withstand the effects of vibration than even the most carefully-welded stop-pins.
With the invention there is also achieved the considerable advantage that the stop-pins can appear with variable length, where a bolt head on the threaded pin can be replaced with a nut which can be adjusted to different positions on the threaded spindle, and hereby determine its different operative lengths. This is of significance since one and the same upper-part is thus able to be used in connection with different under-parts, which while defining the same basic shape of the mould items, are dimensioned with different heights for producing mould items with correspondingly different thicknesses. Consequently, the invention will also involve an innovation regarding an xe2x80x9cadjustable height stopxe2x80x9d between the upper and lower parts of the moulding equipment.
In principle, it is of no importance whether the stop-pins extend downwards from the upper-part or upwards from the lower-part, but for different reasons it is preferred that they extend downwards from the upper-part.
Moreover, for cushioning the shock in connection with the contact of the under-part against the stop-pins in the upper-part, the stop-pins can with advantage comprise shock absorbers of a commonly-known type.